Interferon gamma release assays superior and cost-effective compared with TST

By MedWire Reporters
09 February 2009

Arch Intern Med 2009; 169: 179-187

MedWire News: Two assays used to detect active tuberculosis (TB) and latent TB infections (LTBI) are more effective and less costly than tuberculin skin tests (TSTs), US research shows.

"Our findings are robust and insensitive to changes across a wide range of probabilities, costs, and utility estimates," write Marie de Perio (University of Cincinnati College of Medicine, OH) and colleagues in the Archives of Internal Medicine.

The analysis, modelled in health care workers because of their increased risk of TB infection, compared the cost-effectiveness of two approved interferon gamma release assays (IGRAs), the QuantiFERON-TB Gold test (QFT-G) and the QuantiFERON-TB Gold in Tube test (GFT-GIT).

In this theoretical model, researchers assessed the effectiveness of the IGRAs and TST in a hypothetical 35-year-old female registered nurse working in a US hospital.

The TST strategy was more costly and less effective than either QFT strategy across a wide range of values, including the prevalence of LTBI and the probability of developing active TB, report de Perio and colleagues.

A sensitivity analysis showed that the IGRA strategies were "clinically and economically worthwhile" among low- and high-prevalence populations.

The incremental cost-effectiveness ratio of the QFT-G compared with the QFT-GIT was $14 092/quality-adjusted life-years (QALY) for non–BCG-vaccinated health care workers and $103 047/QALY for BCG-vaccinated health care workers.

TB control in health care settings typically involves screening health care workers for LTBI using the TST, but recent guidelines say the GFT-G can be used in any instance the TST is used.

An advantage of IGRAs over the TST is that they require only a single patient visit, results are available in 24 hours, and the findings are not subject to reader bias.

The study's findings, say the researchers, support the Centers for Disease Control recommendation for using QFT-G when screening health care workers for TB.

MedWire is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

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